When an undersea transmission line is being laid, it is impossible to avoid having to connect two cable ends together, especially during repairs at a point where the cable has been damaged.
An optical fiber undersea cable generally has a core with optical fibers (placed in the tubes of plastics substance which are filled with viscous substances or in helical turns on the periphery of a metal or plastics rod); a cylinder formed by steel wires helically wound and covered by a ductile conductive metal (e.g. copper or aluminium) tube which is longitudinally welded and swaged down over the steel wire arch; an insulating sheath of thermoplastics substance such as polyethylene.
The connection between two cable ends thus constituted is difficult to provide, since said connection performs three distinct functions:
end-to-end connection of the optical fibers of both cables, leaving a sufficient excess length to avoid breakage of the fibers under the effect of unexpected traction; PA1 mechanical continuity of the arches of steel wires which provide the cable with its tensile strength; and PA1 watertight sealing against the high pressure prevailing at great depths.
In accordance with suggestions previously made, such connections have already been described by the Applicant. These connections have: fixing parts on which the ends of cables are fixed; a mandrel on which the excess length of optical fiber is wound; a container tube which surrounds the mandrel and which mechanically connects the fixing parts. Said configuration therefore obliges the operator to firstly connect the optical fibers and then to mechanically connect the ends of the cables. This obviously presents a danger of breakage.
Preferred embodiments of the invention make it possible to remedy said disadvantage by producing a connection which makes it possible firstly to mechanically connect the cable ends and secondly to connect the optical fibers without danger of breaking them accidentally or by improper operation.
Preferred embodiments of the invention also provide a simple connection and method to allow the connection to be wound onto a davit while providing high mechanical strength, proper sealing by means of a water-repellent substance and good electric insulating by using sheaths made of thermoplastic substances.